Signaling loop including railroad tracks



Nov. 14, 1967 G. w. GRAY 3,353,018

' SIGNALING LOOP INCLUDING RAILROAD TRACKS Filed Mar ch 19, 1965 10 i z 7 j v I P 4 z0- .fzz /2 wan/am: 1 9 6144/1/65 ova/14m? INVENTOR 620:6: W 604) if W19 91% United States Patent 3,353,018 SIGNALING LOOP INCLUDING RAILROAD TRACKS George W. Gray, Lamhertville, N.J., assignor to Radio Corporation of America, a corporation of Delaware Filed Mar. 19, 1965, Ser. No. 441,088 5 Claims. (Cl. 246-34) This invention relates to apparatus for the direction and control of and communication to a vehicle which runs on conductive tracks and particularly to signaling loops comprising a part of the conductive tracks.

When using the inductive type of train detection, it has been suggested to provide a loop of wire between or beneath the railroad tracks, so that when a railroad vehicle runs over the loop, the inductance thereof decreases. Such loops however have the disadvantage of being subject to mechanical damage by the train passing over the tracks or by a flame thrower used to clear snow, ice and weeds. Furthermore, since the tracks or rails are electriclly coupled to such loops, a distant railroad vehicle on the rails can cause the loop to give a false indication whereby provisions must be made to prevent such false indication.

It is an object of this invention to provide an improved loop suitable for detection of railroad vehicles passing over a track.

It is another object of this invention to provide an improved detection and signaling loop for a railroad requiring a minimum of modification of existing tracks. Another object of this invention is to provide an improved detection and signaling loop for railroad track requiring less care and maintenance than existing detection and signaling means.

According to this invention, an insulated joint is provided in one rail of a pair of railroad tracks. The two rails are connected to each other by conductive connectors running substantially perpendicular to the rail at two positions which are spaced-from the insulated joint on opposite sides thereof thereby completing the loop. The inductance of the loop is varied by metal parts of the vehicles comprising a train passing over the loop and also by the short circuit produced when the rails comprising part of the loop are connected together by the wheels and axles of the rail-road vehicle passing over the loop. Measurement of the change in inductance may be made by connecting electrical leads to the rail at each side of the insulated joint.

The novel features of the invention both as to its organization and method of assembly, as well as additional objects and advantages thereof, will be understood more readily from the following description when read in conjunction with the accompanying drawing in which FIGURE 1 is a diagrammatic showing of the detection loop of this invention, and

FIGURE 2 is a sectional view of FIGURE 1 along line 2-2 thereof.

An insulated joint is provided in one of the rails 12 of a portion of a pair of rails 12 and 14. A pair of conductive connections 16, 16 are made between the rails 12 and 14 at spaced distances in opposite directions from the joint Ill, completing the loop 15. For optimum operation of the loop 15, the joint 10 should be midway be tween the connections 16, 16. These connections 16, 16 extend substantially perpendicular from the rails 12 and 14, and they can each consist of a heavy stranded copper wire connected to a conductive plug or pin 18 at each end thereof. The two plugs 18, 18 at each end of each c0nnector 16 can be driven respectively into holes in the web of each rail 12 and 14 and the wires between the rails 12 and 14 can lie below the surface of the ties (not shown) on which the rails 12 and 14 are laid.

For coupling a utilization device such as inductance change measuring equipment 19 to the loop 15, a pair of leads 20, 22 are respectively connected between the portions of the rail 12 at each side of the insulated joint 10 and the terminals of theequipment 19. For optimum operation, the distances of the leads 20 and 22 to the joint 10 should be substantially equal, and the leads 20 and 22 should be between the pins 18 and the insulated joint 10.

In explanation of the operation of the described loop 15, let it be assumed that a railroad vehicle (not shown) including a conductive wheel and axle assembly 24 is on the rails 12 and 14 approachingthe loop 15 but on one side of both of the connectors 16, 16. This assembly 24 will then provide a connection between the rails 12 and 14 and also a mass of conductor outside of the loop 15. The connection between the rails 12 and 14 provided by the connectors 16, 16 will prevent the wheel assembly, while outside the loop 15, from having any substantial effect on the inductance thereof. As soon as the wheel assembly 24 moves onto the rails 12, 14 between the connectors 16, 16, the size of the loop will be decreased by the connection across the rails 12 and 14 provided by the wheel assembly '24, decreasing the inductance of the loop 15. Also, the presence of the conductive mass of the wheel assembly 24 or of other partsofthe railroad vehicle in the area of the loop 15 decreases the inductance thereof. Since the inductance of the loop 15 is decreased by either the connection between the rails provided by the wheel assembly 24 or by the effect of the conductive mass in the area of the loop, the described loop 15 will detect the presence of a railroad vehicle Within the loop area whether the wheel assembly makes good contact between the rails or not.

The inductance change caused by a railroad vehicle 'passing over the loop 15 is detected, by the inductance change detector 19. The detector 19 can comprise a portion of a tuned circuit, whereby the phase of a given Wave applied to this tuned circuit is varied by changes in the inductance of the loop 15. The phase changed wave is compared to a given wave whose phase is not changed to detect the presence of a vehicle in the loop 15. If the loop 15 is to be used for communication, a transmitter and receiver may be substituted for the inductance change detector 19. Another loop (not shown) can then be carried on each railroad vehicle with which communication may be desired, and this other loop may itself be connected to a transmitter and receiver on the vehicle. The loop on the rail vehicle and the railroad loop 15 will be coupled when the vehicle passes close to the railroad loop 15 whereby communication with a moving railroad vehicle is made possible.

Since only one insulating joint is required in the loop 15, modification on the track to provide the loop 15 is kept at a minimum. Since only two connections 16, 16 are required between the rails 12 and 14 to complete the loop, less structure in addition to the tracks is required that is subject to damage and needs maintenance than in prior art loops used with rails.

Although only a single loop structure has been shown and described, variations are possible within the spirit of the present invention. For example, any type of conductor or any means for making electrical connection between the ends of the conductors and a track can be used instead of the connectors 16 and their plugs 18. Hence it should be understood that the foregoing description is to be considered as illustrative and not in a limiting sense.

What is claimed is:

1. A railroad signaling and detecting loop system comprising:

a portion of a pair of rails,

an insulating joint in one of said rail portions,

a pair of connectors connecting said rail portions at positions spaced at opposite sides of said insulating joint, said connectors running substantially perpendicularly to said rail portions,

a pair of leads,

a utilizing device having a pair of terminals,

said leads being connected between respective points on said one rail at opposite sides of said insulated joint and respective ones of said terminalsof said utilization device.

2. A railroad signaling and detecting loop system comprising:

a portion of a pair of rails,

an insulating joint in one of said rail portions,

a pair of connectors connecting said rail portions at positions spaced at opposite sides of said insulating joint, said connectors running substantially per-.

pendicularly to said rail portions, a pair of leads, a utilization device having a pair of terminals, the first of said pair of leads being connected to a point on said one rail between said insulated joint and one i of said connectors and to one terminal of said device,

the second of said leads being connected to a point on said one rail between said insulated joint and the other of said connectors and to the other terminal of said device.

3. A railroad signaling and detecting loop system comprising:

a portion of a pair of rails,

an insulating joint in one of said rail portions,

a pair of connectors connecting said rail portions at positions equally spaced at opposite sides of said insulating joint, said connectors running substantially perpendicularly to said rail portions,

a pair of leads,

a utilization device having a pair of terminals,

the first of said pair of leads being connected to a point on said one rail between said insulated joint and one of said connectors and to one terminal of said device,

the second of said leads being connected to a point on said one rail between said insulated joint and the other of said connectors and to the other terminal of said device.

4. The railroad signaling and detecting loop system of claim 5 in which said utilization devicecomprises inductance change measuring equipment.

5. A railroad signaling and detecting loop system comprising:

a portion of a pairof rails, there being an electrical discontinuity in one of said rail portions,

a pair of connectors connecting said rail portions at positions spaced at opposite sides of said electrical discontinuity, saidconnectors running substantially perpendicularly to said rail portions,

a pair of leads,

a utilization device having a pair of terminals,

said leads being connected between respective points of said one rail at opposite sides of said electrical discontinuity and respective ones of said terminals of said utilization device.

References Cited UNITED STATES PATENTS OTHER REFERENCES Doble: Presence Detectors Can Aid Track Circuits,

Railway Signaling and Communications (RSC), June 1963, pp. 30-32 and 34.

ARTHUR L. LA POINT, Primary Examiner.

STANLEY T. KRAWCZEWICZ, Examiner.

S. B. GREEN, Assistant Examiner. 

5. A RAILROAD SIGNALING AND DETECTING LOOP SYSTEM COMPRISING: A PORTION OF A PAIR OF RAILS, THERE BEING AN ELECTRICAL DISCONTINUITY IN ONE OF SAID RAIL PORTIONS, A PAIR OF CONNECTORS CONNECTING SAID RAIL PORTIONS AT POSITIONS SPACED AT OPPOSITE SIDES OF SAID ELECTRICAL DISCONTINUITY, SAID CONNECTORS RUNNING SUBSTANTIALLY PERPENDICULARLY TO SAID RAIL PORTIONS, A PAIR OF LEADS, A UTILIZATION DEVICE HAVING A PAIR OF TERMINALS, SAID LEADS BEING CONNECTED BETWEEN RESPECTIVE POINTS OF SAID ONE RAIL AT OPPOSITE SIDES OF SAID ELECTRICAL DISCONTINUITY AND RESPECTIVE ONES OF SAID TERMINALS OF SAID UTILIZATION DEVICE. 